Over the past few years, I have frequently been asked how to create spot-color artwork from scanned originals. Recently, when I received calls from Maine and Indiana on this question, followed closely by a facsimile message from Malta, I knew it was time to address the subject immediately. There is (as is often the case) no simple solution, no magic program that will handle this task without your intervention and carefully developed skills. But there is a sequence that works very well on some scanned originals and gets you well along with many others.
The core application in this process is Adobe Streamline, a utility that automatically traces scanned images and creates files in Adobe Illustrator format. These files can be opened in most illustration programs. Although many illustration programs include some built-in options for autotracing, none come close to the accuracy or flexibility of Streamline. At a suggested price of $199, this utility will quickly pay for itself in the typical shop. In fact, for most artists, Streamline's fast payback simply comes from its ability to turn scanned logos into editable artwork--the color separation facility is a bonus.
The complete process of converting scanned images into editable artwork consists of several steps, and the software required for each step must be available on your computer system. This software will dictate your choices at each step. But, it is likely that you won't have to acquire anything other than Streamline if you are already engaged in creating artwork on the computer.
Your scanner is normally operated with the software that came with your scanner or with a plug-in module that drives the scanner from either Adobe Photoshop or Aldus PhotoStyler. Scanning is used to acquire an image in digital form, and usually the file is saved as a TIFF-format bitmap, although Streamline also reads PCX-format files. I have found that TIFF is the most stable of the bitmap formats, and have used it exclusively for years. I avoid PCX files because they are not terribly predictable in their assignment of color. Regardless of format, Streamline can open files as large as 16 MB, although you normally won't want to.
While Streamline has a limited set of Photoshop tools built in, most of us are so used to our main image-editing software that we clean up the TIFF in that program, whether it is Photoshop, PhotoStyler, Image Assistant, Photofinish, or Corel PhotoPaint. (Since the merger of Adobe and Aldus, the fate of PhotoStyler is unknown--it will not be sold by Adobe.) My image-editing choice is Photoshop, and I use it every day on my Mac and every week on my PC. This editing step is required to eliminate stray colors and defects in the original image. The artwork you begin with probably will not contain exactly six colors after scanning--there is always some variation in what was meant to be a solid color. Various tools in the image-editing software make it easy to narrow the palette down to the actual colors you will be printing. At this point you still have a bitmap image, which is not useful for spot color work.
This cleaned-up image is then "Streamlined" to generate a vector-format file. Adobe Illustrator is as close as we can get to a universal illustration file format on the computer. However, Streamline can also save files in the DRW format for Micrografx Designer users, HPGL for direct output to plotters, DXF for transfer to CAD software, and CGM and WMF metafiles for placement and printing from other software. The converted file can then be opened in your illustration software.
The conversion options available in Streamline are staggering, but after a few minutes of playing with the sample images that are provided with the program, you should have a pretty good idea of how to handle any given image. The bitmap-to-vector conversion is quick enough that I normally let the program convert the image using the default settings and then fine tune it from there. The program can define all image elements as lines (centerline option) or as shapes (outline options). It can also resolve 2, 4, 8, 16, 64, or 256 colors in the output (up to 16 gray shades). And you have a wide range of control to determine how closely you will trace the original. Tracing tightly with a rough image will yield shapes with a great many points that follow the original's edges very closely. On the other hand, tracing loosely may not follow the shape as accurately, but it will create a far smaller file that can be loaded, edited, and printed quickly.
Your final artwork can be finished and output as separations from whatever illustration program you currently use. Although I don't care much for CorelDRAW! (no surprise to regular readers!), Corel can import Illustrator format easily. (With version 5.0, it can actually export to Illustrator pretty well, too.) Adobe Illustrator itself can be used for finishing and outputting the image, but the current Windows version is pretty dated, a fact that Adobe readily admits. (What is the future of Illustrator for Windows? I've heard nothing at all, but I would predict that Illustrator 6.0 will ship for both Windows and Macintosh at about the same time, maybe even in 1995.) Finally, Aldus FreeHand is generally accepted as the most powerful and flexible tool for creating and working with multiple spot colors, and is my choice for generating and outputting final art for screen printing.
I've used the built-in autotracing features in most of the illustration software on the market, including Corel Trace and several high-end signmaking programs that trumpet their "raster-to-vector conversion." None of them has the flexibility or accuracy of Streamline, and most of them are slower.
My only real problem with Streamline is its method of creating compound objects. If, to take a silly case, you had a black tire with a white hubcap leaning against a red wall in your picture, Streamline would give you a large rectangular red area, with a medium black circle in front of it, with a smaller white circle in front of that. Generating separations that will work for you in this case is more difficult than if the individual colors were separate image areas as opposed to overlapping image areas. But you can duplicate and join the shapes in your illustration to suit your output devices and your trapping requirements.
To recap the conversion process, the sequence is:
I've done some pretty hairy jobs with this sequence. I don't use Streamline often, but when I do, it saves me many hours of work. The user interface is clear and the results are impressive, so you won't need to use Streamline every day to make it a cost-effective addition for your computer design system.
For more information about Streamline 3.0 for Windows or Macintosh, contact:
Adobe Systems
Adobe Systems Incorporated Home Page
1585 Charleston Rd., PO Box 7900
Mountain View, CA 94039
Sales information: 800-833-6687
Faxback service for sales information: 800-235-0078
Now that the new year is here, resolve to send me more questions, comments, samples of successful jobs, or suggestions for future columns. I can't answer every inquiry personally, but I appreciate knowing what you're up against out there, and how you'd like to see the computers you are using (or planning to use) serve you best.